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#include "SkFontHost.h"
#include <math.h>
static void build_power_table(uint8_t table[], float ee)
{
// printf("------ build_power_table %g\n", ee);
for (int i = 0; i < 256; i++)
{
float x = i / 255.f;
// printf(" %d %g", i, x);
x = powf(x, ee);
// printf(" %g", x);
int xx = SkScalarRound(SkFloatToScalar(x * 255));
// printf(" %d\n", xx);
table[i] = SkToU8(xx);
}
}
static bool gGammaIsBuilt;
static uint8_t gBlackGamma[256], gWhiteGamma[256];
#define ANDROID_BLACK_GAMMA (1.4f)
#define ANDROID_WHITE_GAMMA (1/1.4f)
void SkFontHost::GetGammaTables(const uint8_t* tables[2])
{
// would be cleaner if these tables were precomputed and just linked in
if (!gGammaIsBuilt)
{
build_power_table(gBlackGamma, ANDROID_BLACK_GAMMA);
build_power_table(gWhiteGamma, ANDROID_WHITE_GAMMA);
gGammaIsBuilt = true;
}
tables[0] = gBlackGamma;
tables[1] = gWhiteGamma;
}
#define BLACK_GAMMA_THRESHOLD 0x40
#define WHITE_GAMMA_THRESHOLD 0xC0
int SkFontHost::ComputeGammaFlag(const SkPaint& paint)
{
if (paint.getShader() == NULL)
{
SkColor c = paint.getColor();
int r = SkColorGetR(c);
int g = SkColorGetG(c);
int b = SkColorGetB(c);
int luminance = (r * 2 + g * 5 + b) >> 3;
if (luminance <= BLACK_GAMMA_THRESHOLD)
{
// printf("------ black gamma for [%d %d %d]\n", r, g, b);
return SkScalerContext::kGammaForBlack_Flag;
}
if (luminance >= WHITE_GAMMA_THRESHOLD)
{
// printf("------ white gamma for [%d %d %d]\n", r, g, b);
return SkScalerContext::kGammaForWhite_Flag;
}
}
return 0;
}
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